Solid-state (semiconductor-based) image sensors are widely used in cameras or the like. A solid-state image sensor includes a plurality of pixels, which may be two dimensionally arrayed. The pixels employ a photodetector such as a photo diode, Charge Coupled Device (CCD) and/or other photodetectors.
Solid-state image sensors may suffer from a problem that is known as “blooming.” Blooming is a phenomenon that occurs when the number of charge carriers generated in a pixel by the incident light exceeds the charge storage capacity of the pixel. These excess charges may be injected into an adjacent pixel or an adjacent active region, which can degrade performance of the image sensor.
An antiblooming structure for a solid state image sensor is described in U.S. Pat. No. 5,349,215 to Anagnostopoulos et al., entitled Antiblooming Structure For Solid-State Image Sensor. As described therein, solid-state image sensors, in general, comprise a photodetector for detecting radiation from the image and converting the radiation to charge carriers, and transfer means for carrying the charge carriers to an output circuit. One type of solid-state image sensor uses a CCD as both the photodetector and the transfer means. The solid-state image sensor generally includes a plurality of the CCD's arranged in spaced parallel relation to form an array. The image sensor of this disclosure utilizes only one antiblooming lateral overflow barrier. The excess signal charge of phase 1 flows into the preceding phase 2 and is saved. This eliminates the overflow barrier of phase 1 so that blooming protection is via the overflow barrier of the preceding phase 2. This results in an image sensor with blooming protection and increased charge capacity. Antiblooming techniques are also described in also U.S. Pat. Nos. 6,259,124; 6,051,852; 5,867,215; 5,804,844; 5,702,971; and 5,585,298.